1. Field of the Invention
This invention pertains to a fast acting, expansible chamber fluid pump and a diaphragm assembly therefor.
2. Description of the Prior Art
Prior art diaphragms, or bellows are exemplified by a thin sheet of elastomeric resilient material which is intended to be fixedly grasped about its periphery, and which has a central aperture through which extends a motor shaft. Rigid reinforcing plates are secured to one or both sides of an elastomeric sheet and these plates are usually compressed to the sheet by fastener nuts on the motor shaft.
These prior diaphragms and reinforcing plates have presented the metal reinforcing plates in contact with the fluid being pumped. The result is trace quantities of metal in fluids being pumped.
The plate and fastener on the pumped fluid side of the diaphragm also present a crevice around their periphery. This crevice effects carry-over of fluid, trapping of fluid, contamination during periods of non-usage, and presents a cleaning and sanitation problem.
Mechanical fasteners used for retention of the plates to the motor stem usually require a chemical adhesive for reliability, but they still tend to come apart as well as presenting metal to pumped fluid and providing more crevices.
These problems are particularly acute when food products are being pumped. Specific examples of these food products include soft drink syrups, milk, juice concentrates, chocolate and the like. Minute traces of metal effect an off-taste characterized as being metallic, and effect spoilage of the food product. Carry-over of caustic sanitizers effects off-tastes in the food products.
Prior art expansible chamber fluid pumps also do not have sufficiently fast response times to the introduction of propellant fluid. These slow response times are obviously undesirable for dispensing equipment used in fast food establishments.